Chemical compositions are added to fuels and lubricants to control the physical and chemical properties of the fuel and lubricant compositions and to improve engine performance. Such additives include dispersants, antioxidants, viscosity index modifiers, corrosion inhibitors, antiwear agents, friction modifiers, and the like. Dispersants are particularly important additives for lubricant and fuel compositions. Dispersants solubilize sludge, resin and other combustion byproducts so that they can be removed from the system rather than being deposited on internal engine components.
Of the dispersants commonly used in lubricant and fuel applications, Mannich base additives, hydrocarbyl amine adducts, and hydrocarbyl succinic acid derivatives exhibit excellent properties for such applications. Mannich base dispersants are typically produced by reacting alkyl-substituted phenols with aldehydes and amines, such as is described in U.S. Pat. Nos. 3,697,574; 3,704,308; 3,736,357; 4,334,085; and 5,433,875.
Hydrocarbyl succinic acid based dispersants are derived by alkylating, for example, maleic anhydride, acid, ester or halide with an olefinic hydrocarbon to form an acylating agent as described in U.S. Pat. Nos. 5,071,919 and 4,234,435. The acylating agent is then reacted with an amine, typically a polyalkylene amine or amine to form a dispersant, such as described in U.S. Pat. Nos. 3,219,666; 3,272,746; 4,173,540; 4,686,054; and 6,127,321.
Despite the wide variety of additives available for lubricant and fuel applications, there remains a need for improved additives to provide increased deposit control and dispersancy without incurring a cost disadvantage.